Promoting froth flotation



May 15, 1962 R. F. POWELL ET AL PROMOTING FROTI-I FLOTATION 5 Sheets-Sheet 1 Filed April 29, 1959 n W L0 E T O N W REHA O mm MU E =|.LJ.JM. P LJHRE $20525 1525?? Q 8 I. W m M w @w 3 u com 00% 120 com ooom oocm cs9 Inventors Attorneys May 15, 1962 R. F. POWELL ET AL PROMOTING FROTH FLOTATION 5 Sheets-Sheet 2 Filed April 29, 1959 com ooow

LN ILD n wm W mnuR 0 '5 PM H RFTmRE W ooom 002 Inventors Attorneys May 15, 1962 R. F. POWELL ET AL PROMOTING FROTH FLOTATION 5 Sheets-Sheet 3 Filed April 29, 1959 cos s y L L e um M m 0 H ECMM A 0 R .w DIMUM n FEL U M RE nE 3 Q 8 (941) HJNVLLIWSNVHL O CO oQoN

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y 15, 1962 R. F. POWELL ET AL 3,034,648

PROMOTING FROTH FLOTATION Filed April 29, 1959 5 Sheets-Sheet 4 Mi P WELL o o E-ENART co 0 N J. LUR/E a 1w. N/CHOL (A) EDNVLUWSNWL EM BRAND Inventors By WWW/{444w Attorneys May 15, 1962 R. F. POWELL ET AL.

PROMOTING FROTH FLOTATION 5 Sheets-Sheet 5 Filed April 29, 1959 F POWELL F- MARTIN LURIE d NICHDL M- BRAND Inventors- 3 \O EDNVLLIWSNVM 00m 00m 00m e09 320 00$ 00cm coon 003 *M Attorneys United States This invention relates to the use of new chemical compounds as accelerators in the froth flotation of mineral lhe new chemical compounds have the general formula:

o- H Rro \O o-oh wherein R R and R are alkoxy-substituted straight chain alkyl radicals in which the straight chain portion has lto 3 carbon'atoms and the alkoxy subsiituen't also has 1 to 3 carbon atoms.

The process for producing these new chemical com pounds comprises polymerising, in the presence of catalytic quantities of a halogen, one or more substituted aldehydes having 2 to 4 carbon atoms and each containing as a substituent an alkoxy group having 1 to 3 carbon atoms. Depending on whether or not the starting material is a single substance or a mixture of these substances R R and R in the general formula above, may be the same or difierent. Iodine is the preferred catalyst.

The novel substances of this invention are shown by examples given in detail'hereaften to have valuable properties in the art of flotation, when used additionally to known promotors such as xanthates, with or without known frothers being also present; as the more detailed examples show, their net effect is to accelerate the flotation in a concentrate of the particular mineral being floated by the known promotors and frothers. As is wellknown in the art of flotation the effect of a particular reagent differs from ore to ore and it is therefore wellknown to test by standardised well-known procedures the effect both in degree and kind of a particular reagent on a particular ore.

The new chemical compounds of this invention may with some ores show a dominance of their collecting properties and with other ores a dominance of their froth ing properties and the degree of eflectiveness or the said properties will also depend on the particular ore being used. Furthermore the new compounds of this invention can either be used in their purified form or can be used directly as; the reaction product of the reactions set out hereunder by way of example, without purification.

As a method of identification the infra-red spectra of a atent number of these compounds were obtained and are set out in the drawings annexed thereto in which:

FIG. 1 is the infra-red absorption spectrum of 2.4.6- tris-(Z methoxypropyl)-l.3.5-trioxane.

FIG. 2 is the infra-red spectrum of the beta-methoxypropionaldehyde polymer. The sample from which this spectrum was prepared was not quite pure, the impurities showing up in e.g. the absorption at about 2.75 and 5.75 microns;

FIG. 3 is the infra-red spectrum of the beta-ethoxybutyraldehyde polymer;

FIG. 4 is the infra-red spectrum of the beta-n-propoxybutyraldehyde polymer; 7

FIG. 5 is the infra-red spectrum of the copolymer of beta methoxybutyraldehyde and beta ethoxybutyraldehyde referred to below.

Other identifying properties of these substances are given in Table I below.

Purely by way of example and without in any way limiting the generality of the aforegoing some examples will now be given for the purpose of illustrating this invention.

EXAMPLE I Production of 2 .4 .6 -Tris- 2' M ethoxy-Propyl -1 .3 .5 Trioxane 200 mls. of beta-methoxy-butyraldehyde having a water content of less than 0.1% and preferably less than 0.05% is treated with 0.1 gm. of iodine. Heat is liberated and the temperature rises from about room temperature to about 50 C. in approximately 10 minutes. However, it has been noticed that the reaction may continue slowly after this stage.

At the completion of the vigorous reaction or, if-desired, some time thereafter, the reaction product is purified by distillation in known manner to yield the abovementioned new chemical substance which has a boiling point of C. at 0.05 mm. mercury. The structural formula of this substance is:

O CHa CHa-OH-OHr-C EXAMPLE II A. PROCESSES (I) Acetaldehydes: methoxyacetaldehyde and ethoxyacetaldehyde were prepared in known manner and dried in known manner. To each of these substances a catalytic quantity of iodine was added in accordance with the process set out in Example I. An immediate increase in temperature indicated in each case the formation of the polymer. In each case the product was purified by distillation under reduced pressure in known manner and the identifying properties, as set out below, were determined.

(II) Propionaldehyde: beta-methoxypropionaldehyde was prepared and dried in known manner and then subjected to polymerisation according to the process of this invention in the presence of catalytic quantities of iodine. Thereafter the product was purified by distillation under reduced pressure in known manner and the identifying properties set out below, determined.

(III) Butyraldehyde: beta-ethoxybutyraldehyde and beta-n-propoxy-butyr-aldehyde were all prepared and dried in known manner and then each was subjected to the polymerisation process of this invention in the presence of catalytic quantities of iodine. Thereafter the products were purified by distillation under reduced pressure in known manner and the identifying properties set out below, determined.

(IV) A mixture of beta-methoxybutyraldehyde and beta-ethoxybutyraldehyde: 80 m1. of beta-methoxy-butyraldehyde (crude) and 40 ml. of ethoxy-butyraldehyde (crude) were mixed and a catalytic quantity of iodine added. The mixture was allowed to stand overnight and subsequently fractionated under reduced pressure. The major fraction had a boiling point of 104 C. at 0.03 mm. mercury and a molecular weight of 320. This corresponds to the copolymer 2,4 bis-(2' methoxy-propyl)-6- (2' ethoxypropyl)-1,3,5 trioxane which is represented by the following formula B. IDENTIFYING PROPERTIES The following table sets out the identifying properties of the various polymer products prepared as set out above. The molecular weights were determined with the Gallenkamp Semi-micro Ebullio-meter. In this table furthermore the abbreviations R.I.=refractive index; S.G.=specific gravity and the other signs, symbols and abbreviations have their normal meaning to persons-in-the-art.

STANDARD PROCEDURE IN ALL TESTS Crush ore to pass /8 inch screen. Grind 3000 grams ore, 2200 m1. tapwater, 4 grams OaO, for 45 minutes; make up to volume in 10,000

ml. capacity Fahrenwald flotation machine.

pH of pulp is now 7.1.

Add 0.20 lb./ton of sodium-cyanide. 5 minutes.)

Add 0.04 lb./ton of Aerofioat 208.

(Condition for (Condition 2 minutes.)

Add 3 drops (0.018 lb./ton) of commercial T.E.B. (i.e. triethoxybutane) Frother.

Except to Control, add 4 drops (0.024 lb./ton) of polymer being tested.

Float for 60 Seconds. This is Concentrate A Add 4.0 grams CaO. (Condition for 5 minutes.) pH of pulp is now 9.3. Add 0.04 lb./ton potassiumethyl-xanthate. (Condition 2 minutes.)

Except to Control, add 4 drops (0.024 lb./ton) of polymer being tested.

Float for 120 Seconds. This is "Concentrate B Add 0.33 lb./-ton of copper-sulphate. (Condition for 5 minutes.)

Add 2 drops (0.012 lb./ton) of commercial T.E.B. Frother. Except to Control, add 4 drops (0.024 lb./ ton of polymer being tested.

Float for 120 Seconds. This is "Concentrate C (Condition for Float for Seconds. This is Concentrate D" Remaining pulp is discharged and filtered at (T ailings). The detailed results of the control test are set out in Table II showing the method of arriving at the percentage recoveries shown in Table IV. In Table III Table I POLYMERIC ALKOXYALDEHYDES B pt., Pres- M01 M01 I S.G.

0. sure, Weight, W't., C 20/20" 0.

mm. Hg Detd. Theor Polymer of:

Methoxyacetaldehydm 1.0 222 1. 4438 1, 1424 Ethoxyaeetaldehyde 91-92 0 1-0. 2 261 264 1. 4371 1. 0688 Beta-methoxypropionaldehyde. 96 0. 1 265 204 1, 4390 1. 0675 Beta-mothoxybutyraldehyde- 100 0. 05 309 306 1. 4342 1. 0114 Beta-ethoxybutyraldehyde. 0. 05 349 348 1. 4314 0. 9702 Beta-n-propoxybutyraldehyde. 129 0. 05 404 390 1. 4341 0. 9535 Beta-methoxy and beta-ethoxybutyraldehyde 104 0. 03 320 320 1. 4332 1. 0064 EXAMPLE III This example serves to illustrate the accelerating properties on froth flotation processes of the new chemiis set out the key to the nomenclature used in this example with respect to the illustrative members of the new class of chemical compounds according to this incal compounds of this invention. The same ore, a cop- 7 vention which were used in these tests.

Table II Copper Zinc Sulphur Product Percent Percent Percent Percent Percent Percent Percent Weight Assay, Wt. X Recovery Assay, Wt. X Recovery Assay Wt. X Recovery ercent Assay Unlts Cu Percent Assay Units Zn Percent Assay Units S Cu Units Cu Percent Zn Units Zn Percent S Units S Percent of Total of Total ofTotal 7. 23 7. 24 52. 34 41. 4 7.87 56. 90 13. 7 23. 19 167. 7 11. 6 7. 34 3. 79 27. 82 22.0 11.73 86.10 20.7 18.16 183.3 9.2 6.48 2.69 17. 43 13.9 25.29 163.88 39.4 22.69 147.0 10.1 Con D 22. 12 1. 17 25.88 20.5 4.04 89.36 21. 4 29.81 880. 6 60. 8 Cumulative Cons- 43.17 123.47 97.8 296.24 95.2 1, 328.6 91.7 Tails 56.83 0.05 2.85 2.2 0.35 19.89 4.8 2.12 120.5 8.3 Cale. Heads 100 1. 26 126. 32 100 4. 16 146. 13 100 14. 49 1, 449. 1 100 Table 111 Number of Carbon Atoms in Substituted Aldehyde Chemical Name Structural Formula Polymerized of Polymer Straight Alkoxy of R1, R2, R3

Chain Sub- Alkyl stitucnt Radical Thereon M.P.A. Polymer Beta-methoxyprop- 2.4.6 trls (2 methoxy 2 1 R R R3 are ionaldehyde. ethyl)-1.3.5-trioxane.

CH O-CH;CH=

E.P.A. Polymer Beta-ethoxyproplon- 2.4.6-trls- (Zethoxyethyl) 2 2 R1, R Ra are aldehyde. 1.3.5-trloxane.

U2H O-CH2CHn P,P.A. Polymer Beta-n-propoxypropi- 2.4.6 tris-(2propoxyethy1) 2 3 R1 R2, R3 are onaldehyde. 1.3.5-trixane.

C3H1OCH2CH M.B.A. Polymer Beta-methoxybutyr- 2.4.6 tris (2 methoxy 3 1 R R R3 are aldehyde. propyl)-1.3.5-trioxane.

CH -CH-CH,-

O CH:

2mo1esBeta-methoxy- 1 R R3 are butyraldehyde 2.4 bis (2 methoxypro- CH CH-CH; M. (E) 3.14. Polymer..- and pyl) -6 (2 ethoxypropyD- 3 and 1.3.5-trioxane. O CH: 1 mole Beta-ethoxybuty'raldehyde. 2 R is CH3CHCHA E.B.A'. Polymer Beta-ethoxybutyr- 2.4.6 -tris (2 ethoxypro- 3 2 R1, R R are aldehyde. py1)-1.3.5-tr1oxane.

CH@CHCH,

P.B.A. Polymer Beta-n-propoxybutyr- 2.4.6- trls (2'propoxypro- 3 3 R1, Ra, R3 are aldehyde. pyl)-1.3.5-trioxane.

CHz-CH-CH,

O CzH- M.A.A. Polymer Methoxyacetalde- 2.4.6 tris (methoxy 1 1 R1, R2, R3 are hyde. methy1)-1.3.5-trioxane. CH H;-

Table IV BUMMARISED RESULTS-PERCENT WEIGHTS [Cum= Cumulative] I Copper Copper-Zinc Zine Con- Pyrites Concen- Middlings A+B centrate A+B+C Concen- A-I-B-l-C-l-D trate (Con- (Concentrate Cum. (Concen- Cum. trate (Con- Cum. centrate A B) trate C) centrate D) PERCENT RECOVERIES-COPPER Copper Copper-Zinc Zine Con- Pyrltes Cale: Ooncen- Middlings A-l-B ccntrate A+B O Concen- A+B+C+D Heads 011., trato (Con- (Ooncen- Cum. (Concen- Cum. trate (Con- Cum. percent eentrate A) trate B) trate O) centrate D) 41. 4 22.0 63. 4 13.9 77. 3 20.5 97. 8 1. 26 \Vltll M P.A. Polymer. 55. 4 22. l 77. 5 l2. 6 90. 1 8. 8 98. 9 1. 29 W'lth E RA. Polymer 36. 8 29. 5 66. 3 20. 36. 3 11. 3 97. 6 1. 18 With P.P.A. Polymer 45.0 26. 9 71. 9 14. 86.4 13.1 99. 5 1. 21 With M.B.A. Polymer 58. 7 23. 6 82. 3 9. 4 91. 7 6. 9 98. 6 1.17 With M. (E)B.A. Po1ymer 38.6 35.0 73.6 10. 7 84.3 11.8 96.1 1.27 With E.B.A. Polymer 49.1 26. 8 75.9 10. 8 86. 7 10.0 96. 7 1.29 With P.B.A. Polymer 36.3 25.2 61.5 16.7 78.2 18.8 97.0 1. 32

PERCENT RECOVERIESZINC Copper Copper-Zinc Z1110 Con- Pyn'tes Cale: Concendlings A+B centrate A+B+G Ooncen- A+B+O+D Heads trate (Con- (Concen- Cum. (Concen- Cum. trate (Con- Cum. Zinc, oentrate A) trate B) trate O) centrate D) percent Control 13. 7 20.7 34. 4 39. 4 73. 8 21. 4 95.2 4.16 With M.P.A. 18. 8 29. 4 48. 2 40. 2 88.2 8. 5 96. 7 4.02 With E.P.A. 14.3 36. 3 50.6 39. 7 90. 3 6. 8 97.1 3. 96 With P.P.A. 14.5 26. 3 40. 8 43. 8 84. 6 11.8 96. 4 3. 96 With M.B.A. 18.9 38. 5 57. 4 34.4 91. 8 5. 3 97. 1 4.00 With M. (E)B. A. Polymer 14.1 34.1 48. 2 39. 7 87. 9 8.1 96.0 3. 87 With E.B.A. Polymer 18.7 34.6 53. 3 36. 2 89. 5 6. 8 96. 3 3.81 With P.B.A. Polymer 14.3 24.0 38. 3 45.0 83. 3 12.7 96.0 4.10

PERCENT RECOVERIESSULPHUR Copper Copper-Zinc Zinc 0on- Pyrites Cale: Ooncen- Middliugs A+B centrate A+B+ G Concen- A+B+C+D Heads sultrate (Con- (Coneen- Cum. (Concen- Cum. trate (Con- Cum. fur, percent centrate A) trate B) trate G) centrate D) V 11. 6 9. 2 20.8 10.1 30. 9 60.8 91. 7 14. 49 14.5 14.8 29. 3 15. 6 44. 0 51.0 95. 9 14.52 Wlth E.P.A. Polymer. 9. 5 16. 8 26.3 18.0 44.3 49. 8 94.1 14. 70 With P.P.A. Polymer. 14.3 16. 2 30. 5 13.1 43. 6 51. 5 95.1 14. 81 With M.B.A. Polymer 16.2 22.0 38. 2 l3. 1 51. 3 45. 2 96. 5 14.41 W'ith M. (E)B.A. Polymer 11.5 22.1 33.6 11.6 45.2 50.3 95.5 14.61 With E.B.A. Polymer 16. 2 20. 3 36. 5 12. 3 48. 8 46. 5 95. 3 14. 50 With P.B.A. Polymer 10.2 16.2 26.4 16. 1 42. 5 52. 4 94. 9 14.09

These tabulated results will demonstrate clearly to a EXAMPLE IV person-in-the-art the accelerating properties of these new chemical compounds on flotation processes. However, by way of example an analysis is given below of the effects of one of the polymers, namely, M.B.A. polymer compared to the control without polymers.

Note, firstly, that for only 2.43% extra weight, 17.3% extra copper is recovered in the copper pull (Con. A), but only 5.2% extra zinc; in the copper-zinc-middlings pull (Con. B), a relatively large increase of 12.16% extra weight recovers only 1.6% extra copper, but 17.8% extra zinc; in the zinc-pull (Con. C), a small increase of 1.37% extra weight recovers 4.5% less copper (because progressively 18.9% extra copper had already been recovered in Cons. A+B), and 5.0% less Zinc (because progressively 23.0% extra zinc had ready been recovered in Cons. A+B).

Looking at the other end of the series of operations, the final bulk concentrate of high-grade pyrites (Con. D) was 4.37% less in weight, but contained in it was 13.6% less of the copper, and 16.1% less of the zinc.

The overall loss of copper in the tailings was 0.8% less, and of zinc 1.9% less.

These results clearly demonstrate the characteristic effect of using these chemicals as additives, all other reagents and procedures being identical. This elfect is a speeding-up or acceleration of flotation of the particular mineral for whose flotation conditions are correct.

Those skilled in the art will be able to devise plant procedures that make the best use of such effects to give improved metallurgical results.

As an illustration of the observed effects obtained by using the new chemical compounds of this invention as accelerators in flotation processes a report is set out in this example of a preliminary test using the M.B.A. polymer in addition to normal promoter and frother on a gold bearing arseno-pyrite ore-concentrating plant. I

A feature of the plant was a unit cell included in th grinding circuit, and as it was felt that this would be an ideal place to observe the elfects, the accelerator was added to the pump sump immediately before the unit cell.

It was observed that the froth texture and depth changed immediately, becoming much tougher, also showing signs of intense mineral flocculation. As the froth became tougher it appeared that considerable coarser material was being retained and in addition that more slimed graphite and arseno-pyrite was being lifted at this stage.

The rate of addition of accelerator was increased from about 011 lb. per ton ore to about double, and instead of running the froth became tougher still, the mineral building up to an extent that additional frother (T.E.B/ Pine Oil) and promotor Aerofloat 25 had to be used to get the froth moving.

It appeared at this stage that the grade was down slightly but by the amount of material removed the recovery must have increased.

Once this section had settled down, a second reagent feeder was set up over the conditioner to the roughing bank and additional accelerator added at this point.

Similar .eflfects were noticed-bubble texture changed to a smaller more persistent bubble, and the froth toughened up. The load consisted of some fairly coarse material and much slimed graphite and arseno-pyn'te.

10 EXAMPLE v1 Reagents E.B.A. Polymer and M.B.A. Polymer Versus Control With T.E.B./Pine Oil on a Barberton Pyrite It was this slimed graphite and arseno-pyrite that gave 5 0 H 89 the most lnterestlng picture. The colour of the cells became much darker than before and the scavengers much A DnVePFahrenwa1d machm? of htfe P Y a lighter in colour, this latter being most unusual. In other used Wlth an aqueous Ore P p 111 the manner known to words the more sluggish material was coming up cel PBTSOHS Skilled in he ar Starvation quantities used, and its rate of flotation increased i.e. accelerated. 10 0.018 1b./ ton of ore, to P11 a conc n ra e i 15 minu s.

PLE V Sodium sec.-buty1xanthate used as 'a promoter.

This example will illustrate that although certain of f P1ymer 74'7% of pyrites floated grade the new compounds of this invention e.g. M.B.A. polymer, which from Examples III and IV above is clearly an 15 Polymer-"805% of Pymes flQated grade excellent accelerator, do act as very good frothers in water, 32-96% nevertheless the accelerating properties of the new com- Control-.64.9% of pyrites floated grade 36.35% S. pounds of thls lnventlon are not necessarily dependent Far the best depth of froth was given by Po1y on their ablllty to form a froth 1n water. mer In th 0 Se fEB A 01m r d M B A 1 The following tests were conducted in a Denver-Fahrene i o p e an P0 ymer W81 d machine of 10 litre capacity m neral-collectlng power was ev1dent, as well as powerful 30 drops (:0.27 ml.) of unreacted beta-methoxy-' fmthmg efiects' butyraldehyde were added to 10 litres of Water, and upon EXAMPLE VII aeration very little froth was formed.

However, in a comparative test the addition of as little Reagent M.B.A. Polymer Versus Control With (a as 2 to 4 drops (0.010 to 0.030 ml.) of the M.B.A. polyblend of Triethoxybumne and Triethoxyhexanle) on mer gave, upon aeratlon, copious volumes of froth of a P rites Gold Bearin Residues From c (Inflation desirable type. These tests demonstrated water frothing i 5 8, g y l powers of these 2 materials.

A similar test with unreacted beta-ethoxy-butyralde- S t 1 th t d t hyde required over 20 drops (0.18 ml.) to give, upon aera- 0 mm see u y Kan a 8 use as promo or) tion, an appreciable volume of froth, whereas as little as 4 drops (0.036 ml.) of the E.B.A. polymer gave, upon s gg zg gg g l gg 3 5 3 g g ffi xg aeration, copious volumes of froth of a desirable type. 5 Y 9 p an e The polymer however is completely water S01u to persons shllled 1n the art. 0.040 1b.{ton of residues ble and has no visible effect on the water in the standard of Pi floated We1ght of concen Water frothing test. Nevertheless, when submitted to the Hates cofltalnmg O the pyr1tes, and 59.0% of ore tests according to Example III it clearly showed the e dton of d q 37 X, floated accelerating effect as will be apparent from Table V below 5 5 Welght 0f cencentl'ates ng .6% of the in which the results are set out in the same manner as '40 pyrites, and 48.0% of the gold. In this test the frothlng in Table IV above. power of M.B.A. polymer was predominant.

Tqble V PERCENT WEIGHTS 0011A ConB A-l-B Con o A+B+C ConD A+B+C+D Cum. Cum. Cum.

Control 3. 3 3. 4 6. 7 4. 1 10. 8 23. 6 34. 4 With M.A.A. Polymer 4.8 5.1 9. 9 6. 8 16. 7 25. 2 41. 9

PERCENT RECOVERIES COPPER A+B A+B+C A+B+G+D Cale: OonA ConB Gum. 0011 0 Cum. ConD Cum. Heads Cu,

percent Control 29.2 21.1 50.3 11.7 62.0 36.0 98.0 1.25 With 04.11.11. Polymer 36.0 20.3 56.3 12.0 68.3 28.1 96.4 1.37

PERCENT RECOVERIES ZINC A+B A+B+ A+B+C+D Cale: OonA ConB Guru. 0011 0 Cum. ConD Gum. Heads Zn,

Control 8.2 9.7 17.9 32.4 50.3 43.8 94.1 3.98 With M.A.A. Polymer 11.2 13.6 24.8 47.0 71.8 24.6 96.4 3.98

PERCENT RECOVERIES SULPHUR A+B A+B+C A+B+O+D Cale: Con A 0011 B Gum. 0011 0 Cum. Oon D Cum; Heads 8, percent Control 5.6 5.8 11.4 7.5 18.9 66.9 85.8 14.60 WithM.A.A. Polymer 8.9 8. 5 17.4 11.4 28.8 06.3 95.1 14.62

1 1 EXAMPLE vnI Reagents M.B.A. Polymer and E.B.A. Polymer plus T.E.B./Pine Oil Versus Control With T.E.B./Pine Oil Alone, on a Transvaal Ore Containing Arseno-pyrite and Gold (0.9% As: 12 dwts. Au) pH 7.2

A Denver-Fahrenwald machine of litre capacity was used with an aqueous ore pulp in the manner known to persons skilled in the art.

In these tests neither M.B.A. polymer nor E.B.A. polymer had any true frothing properties: froths had to be produced by means of the T.E.B./ Pine Oil mixture whether or not the M.B.A. polymer or E.B.A. polymer was Percentage Recoveries Control:

56.8% of the As and 65.9% of the Au in first concentrate 63.2% of the As and 70.4% of the Au in first and second concentrates 84.9% of the As and 91.5% of the Au in total concentrates M.B.A. Polymer 0.048 lb./ton ore additionally:

85.9% of the As and 89.0% of the Au in first con centrates 90.0% of the As and 92.4% of the Au in first and second concentrates 91.6% of the As and 93.8% of the An in total concentrates E.B.A. Polymer 0.048 1b. /ton ore additionally:

77.4% of the As and 83.1% of the Au in first concentrate 85.1% of the As and 90.8% of the Au in first and second concentrates 87.5% of the As and 93.0% of the An in total concentrates 12 What is claimed is: 1. In froth flotation of mineral ore with the aid of a promoter, the addition to the froth flotation medium of a compound of the formula wherein R R and R are alkoxy-substituted straight chain alkyl radicals in which the straight chain has from I to 3 carbon atoms and the alkoxy substituent also has from 1 to 3 carbon atoms.

2. A process according to claim 1 wherein the said compound is 2.4.6-tris-(2' methoxypropyl)-1.3.5-trioxane.

3. A process according to claim 1 wherein the said compound is 2.4.6-tris-'(2' ethoxypropyl)-1.3.5-trioxane.

4. A process according to claim 1 wherein the said -.compound is 2.4.6-tris-(2' propoxypropyl)-1.3.5-trioxane.

5. A process according to claim 1 wherein the said compound is 2.4.6-tris-(2' methoxyethyl)-1.3.5-trioxane. 6. A process according to claim 1 wherein the said ,compound is 2.4-bis-(2 methoxypropyl)-6-(2' ethoxypropyl -1.3 .S-trioxane.

7. A process according to claim 1 wherein the said compound is 2.4.6-tris-(methoxymethyl)-1.3.5-trioxane.

8. A process according to claim 1 wherein the said compound is 2.4.6-tris-(ethoxymethyl)-1.3.5-trioxane.

References Cited in the file of this patent UNITED STATES PATENTS 2,347,447 Walker Apr. 25, 1944 2,465,489 Sokol Mar. 29, 1949 2,561,251 Van Aardt July 17, 1951 2,770,654 Trapp Nov. 13, 1956 2,901,107 Fischer Aug. 25, 1959 2,904,177 Michal Sept. 15, 1959 OTHER REFERENCES Trioxane, Walker and Carlisle, Chemical and Engineering News, volume 21, number 15, August 10, 1943, pages 1250 and 1251. 

1. IN FROTH FLOTATION OF MINERAL ORE WITH THE ACID OF A PROMOTER, THE ADDITION TO THE FROTH FLOTATION MEDIUM OF A COMPOUND OF THE FORMULA 